A Study on the Combustion Characteristics of a Methane Jet Flame in a Pressurized Hot Vitiated Co-flow

This work presents the study of the methane jet flame in a pressurized vitiated co-flow burner (PVCB). The lift-off length and the stabilization of the methane jet flame under different environment pressures, co-flow temperatures, co-flow rates and jet velocities have been studied, and a chemical numerical simulation based on Gri-mech 3.0 was analyzed as well. The results could provide theoretical supports for the research of natural gas engine combustion stabilization control to increase its thermal efficiency. The experimental results show that the lift-off length decreases obviously (104.22mm to76.14mm) with the increase of the environment pressure (1to1.5bar, 1073K) and temperature (119.34mm to 43.74mm from 1058K to 1118K, 1bar), meanwhile, it also increases with the increment of the co-flow rate and jet velocity. The stabilization of the lift-off length tends to be better and the methane jet flame tends to be brighter with the lift-off length decreasing under all operation conditions. The results indicated that the lift-off length and the stabilization of methane jet flame are sensitive to the co-flow temperature and the environment pressure. By the numerical simulation, the auto ignition delay of the methane decreases with the increase of the environment pressure and co-flow temperature is observed, the minimum auto-ignition temperature of the methane/air pre-mixture decreases with the environment pressure increases. The numerical results showed temperature and environment pressure are the key factors resulting in the decrease of the lift-off length. It indicated that the increment of the environment pressure could promote the combustion reaction.